As a method for producing an electrode assembly to be used as an electrode of a lithium-ion battery, for example, PTL 1 discloses a method for producing an electrode assembly including a step of forming a first solid electrolyte in a plurality of voids of a porous active material molded body containing a lithium composite oxide, and a step of impregnating a precursor solution of an amorphous second solid electrolyte which conducts lithium ions into the active material molded body in which the first solid electrolyte is formed, followed by a heat treatment, thereby forming the second solid electrolyte in the plurality of voids.
It is said that by using the thus produced electrode assembly, the plurality of voids of the active material molded body are filled with the first solid electrolyte and the second solid electrolyte, and therefore, a lithium-ion battery capable of obtaining sufficient output and increasing the capacity can be obtained.